1. Field of the Invention
The present invention relates to a thermal fixing device and an image forming apparatus including the thermal fixing device.
2. Description of the Related Art
An image forming apparatus such as a laser printer is generally provided with a thermal fixing device for thermally fixing a toner transferred on a sheet.
Such a thermal fixing device includes a heat roller, a pressure roller disposed to face the heat roller and for pressing a sheet to the heat roller, and a pair of conveyance rollers disposed to face each other at a conveyance direction downstream side of the sheet with respect to the heat roller and the pressure roller and for conveying the thermally fixed sheet.
The sheet on which a toner is transferred enters between the heat roller and the pressure roller so that the toner on the sheet comes in contact with the heat roller, and the sheet is heated under pressure between the heat roller and the pressure roller so that the toner on the sheet is melted and thermally fixed, and then, the sheet enters between the pair of transfer rollers and is ejected while being held between the conveyance rollers.
However, in the thermal fixing device as stated above, since the sheet is heated under pressure between the heat roller and the pressure roller, the sheet having passed through between the heat roller and the pressure roller becomes apt to get a curl having the same shape as the circumferential shape of the heat roller. Then, a jam occurs when the sheet having the curl enters between the pair of conveyance rollers.
In order to overcome the above problem, there is proposed a technique that a guide member for guiding a sheet or the like sent out by a fixing rotation body toward a direction in which an upward curl is not cancelled out is provided between the fixing rotation body and a paper ejecting rotation body pair, the front end of the sheet or the like separated from the guide member is hung down by its own weight so that it is curved in the opposite direction to the direction of the curl, and the front end of the sheet or the like curled upward is guided to a nip part of the paper ejecting rotation body pair (see Japanese Utility Model Registration No. 2512664).